It is known in the art to pass harvested materials, such as hay, through multiple sets of paired, oppositely rotating rolls in an effort to condition, crush, and/or macerate the stems of the crop materials. See, for example, U.S. Pat. No. 6,050,070 issued to Ivan J. Cook on Apr. 18, 2000. See also a commercially available machine sold under the trade name and mark MACERATOR 6600 by AgLand Industries Inc. of Arborg, Manitoba Canada. However, for a variety of reasons, the prior art systems have not been entirely satisfactory.
The present invention provides a novel method and apparatus for obtaining improved crop conditioning. It also provides greater flexibility for the operator to choose the degree of conditioning to which the crop materials will be subjected. In a preferred form of the invention, two sets of paired, oppositely rotating rolls are used, with the front pair comprising a pair of non-compressible, metal rolls having longitudinally extending helical ribs about their periphery to perform a conditioning and feeding action. The ribbed metal rolls feed the conditioned materials directly to a rear pair of counter-rotating compressible surface rolls having longitudinally extending, relatively wide helical bars about their periphery. Like the narrow ribs on the front rolls, the wide bars on the rear rolls intermesh so as to provide an aggressive conditioning action as the crop materials pass between the rear rolls. Each set of rolls can be readily adjusted to control the tension force maintained on the rolls and the gap between the rolls.
The tension mechanism for the rolls includes a hydraulic circuit that utilizes at least one hydraulic cylinder connected to a moveable roll of each pair. The circuit containing the cylinder may be pressurized up to a certain selected level and then maintained at such level by closing a control valve to trap fluid against escape to the reservoir. Preferably, a compressible gas accumulator is connected in parallel fluid flow relationship with the cylinder to provide a yieldable, cushioning effect. The tension on the front rolls can be adjusted separately from the tension on the rear rolls. The front and rear rolls are mounted in such a way that the front rolls can move apart independently from the rear rolls and vice versa.